This invention relates to drill bits, more specifically to improvements in roof drill bits for drilling and boring in roof bolting operations for mining.
Such cutting elements are often subjected to intense forces, torques, vibration, high temperatures and temperature differentials during operation. As a result, stresses within the bit may begin to form. Drag bits for example may exhibit stresses aggravated by drilling anomalies during roof boring operations such as bit whirl or bounce often resulting in spalling, delamination or fracture of the super hard abrasive layer or the substrate thereby reducing or eliminating the cutting elements efficacy and decreasing overall drill bit wear life. Damage typically found in drag bits may be a result of shear failures, although non-shear modes of failure are not uncommon.
Roof bolt bits have been disclosed in the patent prior art. U.S. Pat. No. 5,535,839 by Brady et al., which is herein incorporated by reference for all that it contains, discloses a roof bit that has two hard surfaced inserts having domed working surfaces.
U.S. Pat. No. D529,937 by Brady et al., which is herein incorporated by reference for all that it contains, discloses the design for a heavy duty roof drill bit.
U.S. Pat. No. 5,848,657 by Flood et al, which is herein incorporated by reference for all that it contains, discloses domed polycrystalline diamond cutting element wherein a hemispherical diamond layer is bonded to a tungsten carbide substrate, commonly referred to as a tungsten carbide stud. Broadly, the inventive cutting element includes a metal carbide stud having a proximal end adapted to be placed into a drill bit and a distal end portion. A layer of cutting polycrystalline abrasive material disposed over said distal end portion such that an annulus of metal carbide adjacent and above said drill bit is not covered by said abrasive material layer.